Location: Northwest District, Grand Junction Field Office (Mesa County)
Size: 5 acres
Designated: 1987 Grand Junction Land Use Plan
Land Manager: Bureau of Land Management, Grand Junction Field Office, Dominguez-Escalante National Conservation Area
The Gunnison Gravels ACEC was designated in the Grand Junction Field Office RMP (GJFO RMP) of 1987 for its unique geological resources. The surficial geology of the site is composed of the Triassic Kayenta Formation sandstone overlain by Quaternary Alluvium composed of approximately 12,000 cubic yards of sand and gravel. These sediments are believed to have been deposited by the ancestral Gunnison River and possibly the Colorado River 1-5 million years ago before they changed flow directions to their present day alignments.
The river gravel deposit is one of only a few such deposits on the Uncompahgre Plateau along the course of the ancient river system. The ancient river system is believed to have changed to present day alignments due to uplift of the Uncompahgre Plateau with its very hard, erosion-resistant rock diverting the river flows into the softer, more easily eroded rocks of the Mancos Shale.